1. Field of the Invention
The present invention relates to wireless personal communications systems, particularly RF nanocell personal communications systems.
2. State of the Art
Wireless personal communications systems are known as exemplified by published International Application WO 96-41498 entitled Hearing Aid With Wireless Remote Processor, incorporated herein by reference. As described therein, a hearing aid system consists of an earpiece that can be hidden in the ear canal, and which communicates wirelessly with a remote processor unit (RPU). The RPU may be a belt pack, wallet or purse-based unit. Sounds from the environment are picked up by a microphone in the earpiece and sent with other information over a primary two-way wireless link to the RPU, where the audio signals are enhanced according to the user's needs. Signal processing is performed in the RPU rather than the earpiece to take advantage of relaxed size and power constraints. The enhanced audio signals may be combined with other information and transmitted from the RPU over the primary wireless link to the earpiece, where they are converted by a speaker to sounds that can only be heard by the user.
In an exemplary embodiment, communications between the RPU and the earpiece follow an interrogate/reply cycle. The reply portion of the primary wireless link (from the earpiece to the RPU) may use a reflective backscatter technique in which the RPU radiates a carrier signal and the earpiece uses a switch to change between a high backscatter antenna state and a low backscatter antenna state. An additional, optional secondary two-way wireless link can be used for communication between the RPU and a cellular telephone system or other source of information. Furthermore, an RPU keyboard, or voice recognition capabilities in the RPU, can be used to control hearing aid parameters and telephone dialing functions. Two earpieces and an RPU can be used in a binaural wireless system that provides hearing protection and noise cancellation simultaneous with hearing aid functions.
Although the system of WO 96-41498 arises out of the field of hearing health care, as may be appreciated from the foregoing description, the system is more broadly applicable to personal communications in general. Recently, attention has been drawn to the application of wireless personal communications systems to telecommunications and computing. At "ACM97: The Next 50 Years of Computing", for example, the prediction was made that in the future, personal computers will be wrist-sized, accompanied by a pair of reading glasses that present high-resolution images at a comfortable distance. A small, fitted earpiece and a "finger mouse" will be linked to other devices with low-power radio signals. Such a future is not far off.
One of the challenges presented in personal communications systems is to allow multiple such systems to function in close proximity to one another with no performance degradation (or graceful degradation) due to interference. An unofficial benchmark developed by the present assignee to test for robustness of communications in the presence of interference has been the "ten-person hug." That is, ten persons each with a personal communications system of the type described should be able to form a group hug without experiencing significant performance degradation of their respective personal communications systems.
Techniques for avoiding interference in personal communications systems of the foregoing type are described in WO 96-41498, FIG. 6 and accompanying description. Time division multiplexing techniques are used to share bandwidth among different systems. Multiple timeslots (e.g., ten or more) are defined, each timeslot accommodating a single interrogate/reply cycle. Each RPU contains a circuit know as a "sniffer", operational only when the RPU interrogator is not transmitting, that detects the presence of other interrogators. Before an RPU initiates an interrogate/reply cycle, it performs a clear channel assessment procedure in which it listens for other communications. This allows the RPU to determine whether or not other interrogators are nearby, as well as the time intervals during which nearby interrogators are transmitting. A timeslot selection procedure then follows. If no slots are occupied, the RPU is free to initiate an interrogate/reply cycle in any timeslot. If one or more timeslots are occupied but not all, the RPU randomly chooses a timeslot following an occupied timeslot in which to initiate an interrogate/reply cycle. If all timeslots are occupied, the RPU randomly selects a timeslot, repeated times if necessary, and attempts interrogation until interrogation is successful.
The timeslot selection procedure may or may not force other interrogators to change their timeslot selections due to interference, depending on relative geometry considerations. As users move around, their personal communications systems automatically adapt by continually finding new acceptable steady-state solutions using the foregoing time division multiplexing technique.
The foregoing mechanism described in WO 9641498 is relied upon exclusively for avoiding interference of multiple communications devices. This type of "jumping", however, is best described as a "free-for-all," each device jumping to satisfy its own communications needs without regard to other communications devices.
Although the foregoing interference avoidance technique is somewhat successful, it results in rapid degradation as the number of communications devices increases. It is not adequate to assure, to the greatest degree possible, interference-free operation of multiple personal communications systems in close proximity, especially where those personal communications systems may be of diverse types. Various types of personal communications systems are expected to include, among others, hearing health care units, telecommunications headsets, and multimedia headsets.
What is needed, then, is bandwidth management techniques for use in heterogenous wireless personal communications systems that assure, to the greatest degree possible, interference-free operation of multiple, possibly diverse, personal communications systems in close proximity. The present invention addresses this need.